State Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
J Environ Sci (China). 2010;22(10):1527-33. doi: 10.1016/s1001-0742(09)60284-9.
Nanometer zinc oxide (ZnO) powders were used as a catalyst to enhance the ozonation for the degradation of dichloroacetic acid (DCAA) in aqueous solution. The batch experiments were carried out to investigate the effects of key factors such as catalyst dosage, ozone dosage, solution pH and tert-butyl alcohol (t-BuOH) on the degradation efficiency of DCAA. Density functional theory (DFT) was adopted to explore the mechanism of generating hydroxyl radical (*OH) on the ZnO surface. The results showed that adsorption and ozonation processes were not effective for DCAA removal, and the addition of ZnO catalyst improved the degradation efficiency of DCAA during ozonation, which caused an increase of 22.8% for DCAA decomposition compared to the case of ozonation alone after 25 min. Under the same experimental conditions, the DCAA decomposition was enhanced by increasing catalyst dosage from 100 to 500 mg/L and ozone dosage from 0.83 to 3.2 mg/L. The catalytic ozonation process is more pronounced than the ozonation process alone at pH 3.93, 6.88, and 10. With increasing the concentration of t-BuOH from 10 to 200 mg/L, the degradation of DCAA was significantly inhibited in the process of catalytic ozonation, indicating that ZnO catalytic ozonation followed *OH reaction mechanism. Based on the experimental results and DFT analysis, it is deduced that the generation of *OH on the ZnO surface is ascribed to the adsorption of molecule ozone followed by the interaction of adsorbed ozone with active sites of the catalyst surface. It is also concluded that ZnO may be an effective catalyst for DCAA removal, which could promote the formation of *OH derived from the catalytic decomposition of ozone.
纳米氧化锌（ZnO）粉末被用作催化剂，以增强水中二氯乙酸（DCAA）的臭氧化降解。进行了批实验，以研究催化剂用量、臭氧用量、溶液 pH 值和叔丁醇（t-BuOH）等关键因素对 DCAA 降解效率的影响。采用密度泛函理论（DFT）探讨了 ZnO 表面生成羟基自由基（OH）的机理。结果表明，吸附和臭氧化过程对 DCAA 的去除效果不明显，添加 ZnO 催化剂可提高臭氧化过程中 DCAA 的降解效率，与单独臭氧化相比，25 min 后 DCAA 分解增加了 22.8%。在相同的实验条件下，通过增加催化剂用量（从 100 到 500 mg/L）和臭氧用量（从 0.83 到 3.2 mg/L），可以增强催化臭氧化过程。在 pH 值为 3.93、6.88 和 10 时，催化臭氧化过程比单独臭氧化过程更显著。随着 t-BuOH 浓度从 10 增加到 200 mg/L，催化臭氧化过程中 DCAA 的降解明显受到抑制，表明 ZnO 催化臭氧化遵循OH 反应机制。基于实验结果和 DFT 分析，推断 ZnO 表面OH 的生成归因于分子臭氧的吸附，随后是吸附臭氧与催化剂表面活性位的相互作用。还得出结论，ZnO 可能是去除 DCAA 的有效催化剂，它可以促进臭氧催化分解生成的OH 的形成。
